As a device for cooling various heat sources, there has been known an loop heat pipe that includes an evaporator to evaporate working liquid (a liquid phase of a working fluid) by adsorbing heat from a heat source, a condenser to condense vaporized working liquid (vapor phase of a working fluid?) by radiating heat, and a vapor line and a liquid line each connecting the evaporator with the condenser to form a closed loop.
The loop heat pipe is, in principle, a device that does not start up (a device that does not start to serve as a heat transport device; a device, circulation of the working fluid within which is not started) in situations where working liquid does not exists in the evaporator, even if the temperature of the evaporator rises owing to the temperature rise of the heat source. The loop heat pipe is therefore usually configured (installed in an apparatus) so that the height (vertical position) of the evaporator becomes lower than that of the condenser. However, among apparatuses into which the loop heat pipes are installed, there is an apparatus requiring that the evaporator occupies a higher position than the condenser.
Therefore, in order to enable the loop heat pipe having the configuration where the evaporator is located below the condenser to start up, it is proposed to attach a heater to part of the vapor line (a part of the vapor line near the evaporator) and to heat, by using the heater, the part of the vapor line during a prescribed time before activating a heat source (a cooling target).
With a contrivance that enables part of the vapor line to be heated before activating the heat source (when needed to start the loop heat pipe), it is possible to start, the loop heat pipe that is in situations where there exists no working liquid in the evaporator.
However, distribution profiles of the working liquid in the loop heat pipe vary according to the elapsed time after stopping the cooling target, even if the positional relationship between the evaporator and the condenser remains unchanged. Moreover, in the loop heat pipe built into a portable information processing apparatus (a notebook PC (Personal Computer) and the like), distribution profiles of the working fluid vary according to its attitudes while the portable information processing apparatus is carried and/or used. Further, there are cases where heating of the vapor line in short line allows the loop heat pipe to start up, depending on the distribution profile of the working fluid in the loop heat pipe. Consequently, if the heating time of the vapor line is fixed, there arise problems wherein energy more than needed is consumed by heating of the vapor line, the start timing of the cooling target is overdue more than needed, and so on.